California is the toughest state when it comes to vehicle emissions. They have strict standards and they check the emissions that your car emits every two years. Often called a "smog check", this test is needs to be done or can't register your car next registration period. In most other states, a car's emissions are checked every year during an annual inspection. If the car fails the emissions test, then it won't receive a new inspection sticker.

Problem is that lots of cars fail smog and emission tests even when they seem to be in good running shape. To increase the odds that your car will pass the test, there are a few tricks to know. There are also a bunch of myths out there that don't help you much. To help you sort these out, we spoke with a technician at Efird of Florence, a Chrysler, Dodge, Jeep, Ram dealer in Florence, SC, that specializes in emissions testing. He suggests several things that may help you pass the emissions smog test and some that won't do a thing.

Warm up your car before getting it checked

Warming up your car will get your motor running properly and emitting the least emissions. In general, driving your car some 10 or so minutes will warm things up just fine. However, there is a myth running around that says you should sit in your car for 5-10 minutes just before the test running the engine at 3000+ RPM. According to our technician, this is just silly. Your engine is warmed up just fine by driving it normally.

Get a tune-up

This suggestion should be common sense. If your car is not running well, it will likely fail an emissions test. Getting a tune-up will make a vehicle emit fewer emissions and you'll get more miles per gallon.

Adding fuel cleaner help you pass

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Some think this is nutty but there is some truth in this. Using fuel cleaners periodically will help keep your car's engine clean. They burn off the deposits stuck to your engine's valves and head. It's a good idea to use a fuel cleaner relatively often, but it's a bad idea to put it in the car just before you are taking your car to get tested.

Replace the "cat"

Some inspection stations suggest a brand new catalytic converter if you have trouble passing an emissions test.  According to our expert, if your catalytic converter is going bad then by all means replace, it but don't replace it "just because it might help." Often this is just a way for a service station to sell more catalytic convertors.

Pull Out Your "Check Engine" Light

This is one of the silliest things to do. The check engine light is required to be working when the technician tests the vehicle. If the tech doesn't see the light because someone tampered with it—your car will automatically fail the test. If the check engine light in your car comes on, then find out why and get it fixed.


In general, it doesn't make sense to play any tricks to pass an emissions test. If anything isn't working right, get it repaired. Don't put in a new catalytic convertor or pull out the check engine light. If your car doesn't pass, there is likely something that is wrong and should be repaired.